Exposure apparatus and method of manufacturing article

ABSTRACT

The present invention provides an exposure apparatus which transfers a pattern of a mask onto a substrate by exposing the substrate while scanning the mask and the substrate, the apparatus including a stage configured to hold the substrate and move, a control unit configured to control movement of the stage, a first measurement unit configured to measure a position, in a height direction, of a shot region of the substrate held by the stage before the shot region reaches an exposure area where the shot region is exposed, and a second measurement unit configured to measure the position of the shot region in the height direction prior to the first measurement unit.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an exposure apparatus and a method ofmanufacturing an article.

Description of the Related Art

When a semiconductor device or the like is manufactured using aphotolithography technique, a step-and-scan exposure apparatus (scanner)which transfers the pattern of a mask onto a substrate while scanningthe mask and the substrate is used. Japanese Patent Laid-Open No.2014-165284 proposes that a plurality of measurement units which measurethe surface position (height-direction position) of a substrate held bya substrate stage should be provided in such an exposure apparatus.Japanese Patent Laid-Open No. 2014-165284 discloses an exposureapparatus which includes the first measurement unit (read-ahead sensor)measuring a position spaced apart from the projection position of anexposure slit in a scanning direction and the second measurement unit(read-further ahead sensor) measuring a position further spaced apartfrom the projection position of the exposure slit than that of the firstmeasurement unit.

In scanning exposure, fitting of an exposure object area of thesubstrate to an optimum exposure position is performed by the firstdriving in which the substrate stage is driven based on a measurementresult of the second measurement unit and the second driving in whichthe substrate stage is driven based on a measurement result of the firstmeasurement unit. Note that the optimum exposure position is a suitableheight-direction position, and is the best focus position of theexposure slit (image plane) and a position within the range of anallowable depth of focus relative to the best focus position.

In order to improve the productivity of the exposure apparatus, it isconsidered that the scanning speed of the substrate stage in scanningexposure is increased to reduce a time period required for exposure. Inthis case, a time period between measuring the surface position of thesubstrate and starting exposure of the substrate is reduced, making itnecessary to reduce a time period required for fitting of the exposureobject area of the substrate to the optimum exposure position.

On the other hand, in recent years, there is proposed a technique ofstacking a memory cell on a substrate in order to implement an increasein capacity and a reduction in bit cost of a NAND flash memory. However,the flatness of the substrate is decreased, or flatness unevennessoccurs by stacking the memory cell. Consequently, the driving amount ofthe substrate stage required for fitting of the exposure object area ofthe substrate to the optimum exposure position tends to be large.

Therefore, in fitting of the exposure object area of the substrate tothe optimum exposure position, the substrate stage needs to be driven ina shorter time period and by a larger driving amount than before. Ifdriving of the substrate stage is thus controlled, however, thesubstrate stage cannot respond sufficiently, increasing a controldeviation. If the control deviation does not converge at time whenexposure of the substrate is started (that is, the control deviationdoes not fall within an allowable range), that causes an exposure errorby defocus.

SUMMARY OF THE INVENTION

The present invention provides an exposure apparatus advantageous incontrolling driving of a substrate on a substrate stage in a heightdirection.

According to one aspect of the present invention, there is provided anexposure apparatus which transfers a pattern of a mask onto a substrateby exposing the substrate while scanning the mask and the substrate, theapparatus including a stage configured to hold the substrate and move, acontrol unit configured to control movement of the stage, a firstmeasurement unit configured to measure a position, in a heightdirection, of a shot region of the substrate held by the stage beforethe shot region reaches an exposure area where the shot region isexposed, and a second measurement unit configured to measure theposition of the shot region in the height direction prior to the firstmeasurement unit, wherein the control unit controls the stage so as toperform first driving in which the substrate is driven in the heightdirection based on a measurement result of the second measurement unitand second driving in which the substrate is driven in the heightdirection based on a measurement result of the first measurement unitafter the second measurement unit measures the position of the shotregion in the height direction and until the shot region reaches theexposure area, and makes a driving amount of the stage in the heightdirection in the first driving larger than half a distance correspondingto a difference between a final target position of the shot region inthe height direction and the position of the shot region in the heightdirection measured by the second measurement unit.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the arrangement of an exposureapparatus according to an aspect of the present invention.

FIG. 2 is a view showing the relationship between an exposure slit andmeasurement points formed in a shot region of a substrate by measurementunit.

FIGS. 3A to 3D are views for explaining measurement, by the measurementunit, of height-direction positions of measurement object portions in ashot region.

FIGS. 4A to 4C are views for explaining, in detail, measurement of theheights of measurement object portions in shot regions in an exposureprocess.

FIG. 5 is a block diagram for explaining control regarding driving of asubstrate stage in the prior art.

FIGS. 6A and 6B are timing charts for explaining control regardingdriving of the substrate stage in the prior art.

FIGS. 7A and 7B are timing charts for explaining control regardingdriving of the substrate stage according to an embodiment.

FIG. 8 is a block diagram for explaining control regarding driving ofthe substrate stage according to the embodiment.

FIG. 9 is a timing chart for explaining control regarding driving of thesubstrate stage according to the embodiment.

FIG. 10 is a flowchart for explaining the exposure process in theexposure apparatus shown in FIG. 1.

FIG. 11 is a view showing an example of the layout of a plurality ofshot regions on the substrate.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings. Note that the samereference numerals denote the same members throughout the drawings, anda repetitive description thereof will not be given.

FIG. 1 is a schematic view showing the arrangement of an exposureapparatus 100 according to an aspect of the present invention. Theexposure apparatus 100 transfers the pattern of a mask 102 onto asubstrate 104 while scanning the mask 102 and the substrate 104. In anembodiment, the exposure apparatus 100 is a step-and-scan exposureapparatus (scanner) which uses an exposure area of a rectangular or arcslit shape and performs exposure at a large angle of view with highaccuracy by relatively scanning the mask 102 and the substrate 104 at ahigh speed. As shown in FIG. 1, the exposure apparatus 100 includes aprojection optical system 101, a mask stage 103, a substrate stage 105,an illumination optical system 106, a main control unit 127, and ameasurement unit MU.

A Z-axis is defined in a direction parallel to an optical axis AX of theprojection optical system 101, and the image plane of the projectionoptical system 101 is perpendicular to the Z-axis direction. The maskstage 103 holds a mask 102. The pattern of the mask 102 is projected atthe magnification (for example, ¼, ½, or ⅕) of the projection opticalsystem 101, forming an image on the image plane of the projectionoptical system 101.

The substrate 104 is, for example, a wafer whose surface is coated witha resist (photosensitive agent). A plurality of shot regions having thesame pattern structure formed by the preceding exposure process arearrayed on the substrate 104. The substrate stage 105 is a stage whichholds the substrate 104 and moves, and includes a chuck for chucking(fixing) the substrate 104. The substrate stage 105 also includes an X-Ystage which is horizontally movable in the X- and Y-axis directions, anda Z stage which is movable in the Z-axis direction (the height directionof the substrate 104) parallel to the optical axis AX of the projectionoptical system 101. The substrate stage 105 also includes a levelingstage rotatable about the X- and Y-axes, and a rotation stage rotatableabout the Z-axis. The substrate stage 105 therefore constructs asix-axis driving system for making the pattern image of the mask 102coincide with the shot region of the substrate 104. Positions of thesubstrate stage 105 in the X-, Y-, and Z-axis directions are alwaysmeasured by a bar mirror 123 arranged on the substrate stage 105 and aninterferometer 124.

The measurement unit MU has a function of measuring the surface position(height-direction position) and tilt of the substrate 104. In theembodiment, the measurement unit MU measures the height-directionpositions of measurement object portions in the shot region of thesubstrate 104 held by the substrate stage 105. The measurement unit MUincludes two light sources 110, two collimator lenses 111, two slitmembers 112, two light projecting side optical systems 113, two lightprojecting side mirrors 114, two light receiving side mirrors 115, twolight receiving side optical systems 116, two stopper diaphragms 117,two correction optical systems 118, and two photoelectric converters119. The measurement unit MU includes the first measurement unit and thesecond measurement unit each including one light source 110, onecollimator lens 111, one slit member 112, one light projecting sideoptical system 113, one light projecting side mirror 114, one lightreceiving side mirror 115, one light receiving side optical system 116,one stopper diaphragm 117, one correction optical system 118, and onephotoelectric converter 119. The first measurement unit and the secondmeasurement unit are different in position in an X-Y plane to measure.The first measurement unit measures a position spaced apart from theprojection position of the exposure slit in a scanning direction. Thesecond measurement unit measures a position further spaced apart fromthe projection position of the exposure slit than that of the firstmeasurement unit. That is, the second measurement unit measures, priorto the first measurement unit, the height of a shot region to be exposedin the Z-axis direction. Based on measurement result of the measurementunit MU, the substrate stage 105 is controlled in the Z-axis direction,as will be described later. In the control, the first measurement unitand the second measurement unit are switched by a switch SW1 to bedescribed later and used.

Each light source 110 includes a lamp, a light emitting diode, or thelike. Each collimator lens 111 converts light emitted by a correspondingone of the light sources 110 into parallel light whose section has analmost uniform intensity distribution. Each slit member 112 isconstructed by bonding a pair of prisms (prism-shaped members) so thattheir inclined surfaces face each other. A plurality of openings (15pinholes in the embodiment) are formed in the bonded surface by using alight shielding film made of chrome or the like. Each light projectingside optical system 113 is a bi-telecentric system, and guides beamshaving passed through the 15 pinholes of a corresponding one of the slitmembers 112 to 15 measurement object portions in the shot region on thesubstrate 104 via a corresponding one of the light projecting sidemirrors 114.

A plane (bonded surface) on which the pinholes are formed, and a planeincluding the surface of the substrate 104 are set to satisfy a shineproof condition with respect to the light projecting side opticalsystems 113. In the embodiment, an incident angle (angle defined by theoptical axis AX) Φ of light from each light projecting side opticalsystem 113 to the substrate 104 is 70° or more. The 15 beams havingpassed through each light projecting side optical system 113 enterindependent measurement object portions on the substrate and formimages. Light from each light projecting side optical system 113 entersthe substrate from a direction which is rotated by 0° (for example,22.5°) on the X-Y plane from the X-axis direction so that 15 measurementobject portions on the substrate can be observed independently.

Each light receiving side optical system 116 is a bi-telecentric system.The 15 beams (reflected beams) reflected by the respective measurementobject portions on the substrate 104 enter the light receiving sideoptical system 116 via a corresponding one of the light receiving sidemirrors 115. Each stopper diaphragm 117 is arranged in a correspondingone of the light receiving side optical systems 116 and is set commonlyto the 15 measurement object portions. The stopper diaphragm 117 cutsoff high-order diffracted light (noise light) generated by a patternformed on the substrate 104.

The optical axes of the beams having passed through the light receivingside optical systems 116 are parallel to each other. Each correctionoptical system 118 includes 15 correction lenses, and forms the 15 beamshaving passed through the corresponding one of the light receiving sideoptical systems 116 into spot beams having the same size on thephotoelectric conversion surface (light receiving surface) of acorresponding one of the photoelectric converters 119. In theembodiment, the light receiving side optical systems 116, the stopperdiaphragms 117, and the correction optical systems 118 performinclination correction so that the respective measurement objectportions on the substrate and the photoelectric conversion surfaces ofthe photoelectric converters 119 become conjugate to each other. Thus, achange of the position of a pinhole image on each photoelectricconversion surface does not arise from local tilt of each measurementobject portion on the substrate. The pinhole image on each photoelectricconversion surface changes in accordance with a change of the height ofeach measurement object portion in a direction parallel to the opticalaxis AX. Each photoelectric converter 119 is constructed by, forexample, 15 one-dimensional CCD line sensors. However, a plurality oftwo-dimensional sensors may be arranged instead.

As described above, the mask stage 103 holds the mask 102. The maskstage 103 is scanned at a constant speed in the X-axis direction(direction indicated by an arrow 103 a) in a plane perpendicular to theoptical axis AX of the projection optical system 101. At this time, themask stage 103 is scanned so that a position of the mask stage 103 inthe Y-axis direction always maintains a target position (correctiondriving). Positions of the mask stage 103 in the X- and Y-axisdirections are always measured by a bar mirror 120 arranged on the maskstage 103 and an interferometer 121.

The illumination optical system 106 illuminates the mask 102 by usinglight from a light source which generates pulsed light such as anexcimer laser. The illumination optical system 106 includes a beamshaping optical system, an optical integrator, a collimator lens, amirror, a masking blade, and the like. The illumination optical system106 efficiently transmits or reflects pulsed light in thefar-ultraviolet area. The beam shaping optical system forms thesectional shape (dimensions) of incident light into a predeterminedshape. The optical integrator uniforms the light distributioncharacteristic and illuminates the mask 102 at a uniform illuminance.The masking blade defines a rectangular illumination area correspondingto a chip size. The pattern of the mask 102 partially illuminated inthis illumination area is projected to the substrate 104 via theprojection optical system 101.

The main control unit 127 includes a CPU, memory, and the like andcomprehensively controls the respective units of the exposure apparatus100. The main control unit 127 controls the mask stage 103 which holdsthe mask 102, and the substrate stage 105 which holds the substrate 104,in order to form light from the pattern of the mask 102 into an image ina predetermined area of the substrate 104. For example, the main controlunit 127 adjusts, via the mask stage 103 and substrate stage 105, thepositions of the mask 102 and substrate 104 in the X-Y plane (positionsin the X- and Y-axis directions and a rotation about the Z-axis), andtheir positions in the Z-axis direction (rotations about the X- andY-axes). The main control unit 127 scans the mask stage 103 andsubstrate stage 105 in synchronism with the projection optical system101. As described above, the main control unit 127 controls the exposureprocess of exposing the respective shot regions of the substrate 104 inthe exposure area while scanning the substrate 104 by the substratestage 105.

When the mask stage 103 is scanned in the direction indicated by thearrow 103 a, the substrate stage 105 is scanned in a direction indicatedby an arrow 105 a at a speed corrected by the magnification (reductionmagnification) of the projection optical system 101. The scanning speedof the mask stage 103 is determined to be advantageous for theproductivity, based on the width of the masking blade in the scanningdirection in the illumination optical system 106, and the sensitivity ofa resist applied to the surface of the substrate 104.

The pattern of the mask 102 is aligned in the X-Y plane based onpositions of the mask stage 103, substrate stage 105, and respectiveshot regions on the substrate 104 with respect to the substrate stage105. As described above, the positions of the mask stage 103 andsubstrate stage 105 are measured by the interferometers 121 and 124,respectively. The positions of the respective shot regions on thesubstrate 104 with respect to the substrate stage 105 are obtained bydetecting, with an alignment microscope (not shown), the position of amark provided on the substrate stage 105 and the position of analignment mark formed on the substrate 104.

Alignment of the pattern of the mask 102 in the Z-axis direction, thatis, alignment to the image plane of the projection optical system 101 isimplemented by controlling (the leveling stage included in) thesubstrate stage 105 based on the measurement result of the measurementunit MU.

FIG. 2 is a view showing the relationship between an exposure slit 202,and measurement points 203 to 217 formed in a shot region 201 of thesubstrate 104 by the measurement unit MU. The exposure slit 202 is arectangular exposure area indicated by a broken line in FIG. 2. In otherwords, the exposure area is an area in the X-Y plane where the exposureslit 202 is projected. The position of the exposure slit 202 in the X-Yplane is a position facing the final lens of the projection opticalsystem 101. The measurement points 203, 204, and 205 are measurementpoints formed in the exposure slit 202. The measurement points 206, 207,and 208 and the measurement points 212, 213, and 214 are measurementpoints formed at positions spaced apart by a distance Lp1 from theexposure slit 202. The measurement points 209, 210, and 211 and themeasurement points 215, 216, and 217 are measurement points formed atpositions spaced apart by a distance Lp2 from the exposure slit 202. Thedistances Lp1 and Lp2 have a relationship of Lp1<Lp2.

In the embodiment, the measurement points 206, 207, and 208 and themeasurement points 212, 213, and 214 are the measurement points of thefirst measurement unit of the measurement unit MU. The measurementpoints 209, 210, and 211 and the measurement points 215, 216, and 217are the measurement points of the second measurement unit of themeasurement unit MU. In the exposure process, the first measurement unitmeasures the height-direction positions of the measurement objectportions in the shot region 201 of the substrate 104 held by thesubstrate stage 105 before the shot region 201 reaches the exposure slit202. In the exposure process, the second measurement unit measures,prior to the first measurement unit, the height-direction positions ofthe measurement object portions in the shot region 201 of the substrate104.

The main control unit 127 can control the measurement timings of themeasurement points 203 to 217 by the measurement unit MU based on thedistances between the exposure slit 202 and the respective measurementpoints 203 to 217, and the scanning direction and scanning speed of thesubstrate stage 105. The measurement points 203, 206, 209, 212, and 215are formed at the same X-coordinate position. The measurement points204, 207, 210, 213, and 216 are formed at the same X-coordinateposition. Further, the measurement points 205, 208, 211, 214, and 217are formed at the same X-coordinate position. For example, when thesubstrate stage 105 is scanned in the Y-axis direction, the samecoordinate position of the shot region 201 can be measured at differentmeasurement points by adjusting the measurement timings of themeasurement points 203 to 217.

Measurement of the height-direction positions of measurement objectportions in a shot region 301 by the measurement unit MU will bedescribed with reference to FIGS. 3A to 3D. In FIG. 3A, measurementobject positions 302, 303, and 304 indicate positions to be measured inthe shot region 301. There are a plurality of measurement objectportions of the shot region 301 in the Y-axis direction in order tomeasure the height-direction position of the entire shot region 301.However, FIG. 3A shows only the measurement object portions 302, 303,and 304 for simplicity.

For example, a case in which the height-direction position of themeasurement object portion 302 in the shot region 301 is measured byscanning the substrate stage 105 in a direction indicated by an arrow F,as shown in FIG. 3A, will be examined. In a state shown in FIG. 3B, themain control unit 127 controls the measurement timing so that themeasurement unit MU measures the height-direction position of themeasurement object portion 302 at the measurement point 209. In a stateshown in FIG. 3C upon the lapse of a predetermined time period, the maincontrol unit 127 controls the measurement timing so that the measurementunit MU measures the height-direction position of the measurement objectportion 302 at the measurement point 206. Further, in a state shown inFIG. 3D upon the lapse of a predetermined time period, the main controlunit 127 controls the measurement timing so that the measurement unit MUmeasures the height-direction position of the measurement object portion302 at the measurement point 203.

Similarly, a case in which the height-direction of the measurementobject portion 303 in the shot region 301 is measured by scanning thesubstrate stage 105 in the direction indicated by the arrow F will beexamined. In the state shown in FIG. 3B, the main control unit 127controls the measurement timing so that the measurement unit MU measuresthe height-direction position of the measurement object portion 303 atthe measurement point 210. In the state shown in FIG. 3C upon the lapseof a predetermined time period, the main control unit 127 controls themeasurement timing so that the measurement unit MU measures theheight-direction position of the measurement object portion 303 at themeasurement point 207. Further, in the state shown in FIG. 3D upon thelapse of a predetermined time period, the main control unit 127 controlsthe measurement timing so that the measurement unit MU measures theheight-direction position of the measurement object portion 303 at themeasurement point 204.

Similarly, a case in which the height-direction position of themeasurement object portion 304 in the shot region 301 is measured byscanning the substrate stage 105 in the direction indicated by the arrowF will be examined. In the state shown in FIG. 3B, the main control unit127 controls the measurement timing so that the measurement unit MUmeasures the height-direction position of the measurement object portion304 at the measurement point 211. In the state shown in FIG. 3C upon thelapse of a predetermined time period, the main control unit 127 controlsthe measurement timing so that the measurement unit MU measures themeasurement object portion 304 at the measurement point 208. Further, inthe state shown in FIG. 3D upon the lapse of a predetermined timeperiod, the main control unit 127 controls the measurement timing sothat the measurement unit MU measures the height-direction position ofthe measurement object portion 304 at the measurement point 205.

In accordance with a direction (moving direction) in which the substratestage 105 is scanned, the main control unit 127 switches the measurementpoint to be used to measure the height-direction position of ameasurement object portion in the shot region 301. For example,referring to FIG. 2, when the substrate stage 105 is scanned in thedirection indicated by the arrow F, the heights of measurement objectportions in the shot region 201 are measured at the measurement points206 to 211. In contrast, when the substrate stage 105 is scanned in adirection indicated by an arrow R, the height-direction positions ofmeasurement object portions in the shot region 201 are measured at themeasurement points 212 to 217. Based on these measurement results, themain control unit 127 calculates the height-direction position (positionin the Z-axis direction) of an exposure object area including themeasurement object portions in the shot region 201. The main controlunit 127 moves the substrate stage 105 in the Z-axis direction(height-direction of the substrate 104) so that the exposure object areais positioned at an optimum exposure position (final target position)until the exposure object area reaches the exposure slit 202. Note thatthe optimum exposure position is the image plane of the pattern of themask 102, that is, the position (best focus position) of the image planeof the projection optical system 101. However, the optimum exposureposition does not mean a position that completely coincides with theposition of the image plane of the projection optical system 101 butincludes a position within the range of an allowable depth of focus.

Measurement of the height-direction positions of measurement objectportions in shot regions in an exposure process of exposing thesubstrate 104 will be described in detail with reference to FIGS. 4A to4C. FIGS. 4A to 4C are views showing the exposure slit 202, themeasurement points 203 to 211, shot regions 401, 402, and 403,measurement object portions 404, 405, and 406, and the trajectory of thesubstrate stage 105. There are a plurality of measurement objectportions in the shot region 402 in the Y-axis direction in order tomeasure the height-direction position of the entire shot region 402.However, FIGS. 4A to 4C show only the measurement object portions 404,405, and 406 for simplicity. In FIGS. 4A to 4C, the shot region 401 is ashot region having undergone the exposure process. The shot region 402is a shot region to undergo the exposure process next to the shot region401. The shot region 403 is a shot region to undergo the exposureprocess next to the shot region 402. In FIGS. 4A to 4C, an arrowindicated by a broken line represents the trajectory of the substratestage 105 on the X-Y plane.

As shown in FIG. 4A, after the end of the exposure process for the shotregion 401, the substrate stage 105 moves in the X-axis direction whiledecelerating in the Y-axis direction, and moves to the shot region 402to undergo the exposure process next. When the substrate stage 105reaches the acceleration start point in the Y-axis direction (that is,movement in the X-axis direction ends), it is accelerated and moved inthe direction indicated by the arrow F.

As shown in FIG. 4B, when the measurement points 209 to 211 reach themeasurement object portions 404 to 406 in the shot region 402, theheight-direction positions of the measurement object portions 404 to 406are measured at the measurement points 209 to 211. Based on measurementresults at the measurement points 209 to 211 (the height-directionpositions of the measurement object portions 404 to 406), the maincontrol unit 127 obtains the driving amount (target value) of thesubstrate stage 105 in the Z-axis direction to position the exposureobject area at the optimum exposure position. Based on the target value,the main control unit 127 starts the first driving in which thesubstrate 104 is driven in the Z-axis direction by the substrate stage105 (the leveling stage). When the speed (scanning speed) of thesubstrate stage 105 becomes a target speed, the substrate stage 105keeps moving at a constant speed until the exposure slit 202 passesthrough the shot region 402.

As shown in FIG. 4C, when the measurement points 206 to 208 reach themeasurement object portions 404 to 406 in the shot region 402, theheight-direction positions of the measurement object portions 404 to 406are measured at the measurement points 206 to 208. Based on themeasurement results at the measurement points 206 to 208(height-direction positions of the measurement object portions 404 to406), the main control unit 127 obtains the driving amount (targetvalue) of the substrate stage 105 in the Z-axis direction to positionthe exposure object area at the optimum exposure position. Based on thetarget value, the main control unit 127 starts the second driving inwhich the substrate 104 is driven in the Z-axis direction by thesubstrate stage 105 (the leveling stage).

As described above, the main control unit 127 controls, by the firstdriving and the second driving in the exposure process, the substratestage 105 so that a position of the substrate 104 in the Z-axisdirection comes to the optimum exposure position until the shot region402 of the substrate 104 reaches the exposure slit 202. Note that asdescribed above, the first driving represents driving the substrate 104in the Z-axis direction by the substrate stage 105 based on themeasurement results at the measurement points 209 to 211 (secondmeasurement unit). As described above, the second driving representsdriving the substrate 104 in the Z-axis direction by the substrate stage105 based on the measurement results at the measurement points 206 to208 (first measurement unit).

Control regarding driving of the substrate stage 105 to position theposition of the substrate 104 in the Z-axis direction at the optimumexposure position in the prior art will now be described with referenceto FIG. 5, and FIGS. 6A and 6B. FIG. 5 is a schematic block diagramshowing a control system regarding driving of the substrate stage 105.An example to which PID (Proportional-Integral-Differential) control isapplied will be described here. The control system includes a PIDcontroller 501, a filter 502, and a limited driving amount 503 of thesubstrate stage 105.

In FIG. 5, the initial position of the substrate stage 105 is theposition of the substrate stage 105 in the Z-axis direction before thefirst driving or second driving of the substrate stage 105 to positionthe position of the substrate 104 in the Z-axis direction at the optimumexposure position is started. The switch SW1 is a switch which switchesthe measurement points of the measurement unit MU used to measure theheight-direction positions of the measurement object portions in theshot region of the substrate 104. For example, in the first drivingshown in FIG. 4B, the switch SW1 is switched such that the substratestage 105 is driven (controlled) based on the measurement results at themeasurement points 209 to 211 as the second measurement unit. In thesecond driving shown in FIG. 4C, the switch SW1 is switched such thatthe substrate stage 105 is driven (controlled) based on the measurementresults at the measurement points 206 to 208 as the first measurementunit. The PID controller 501 is a controller configured to controldriving of the substrate stage 105 in the Z-axis direction, and includesa P gain (proportional gain), a D gain (derivative gain), and an I gain(integral gain). If the driving amount of the substrate stage 105 inputfrom the filter 502 is equal to or smaller than the limited drivingamount 503, the driving amount is output without any change. On theother hand, if the driving amount of the substrate stage 105 input fromthe filter 502 is larger than the limited driving amount 503, thelimited driving amount 503 is output as the driving amount of thesubstrate stage 105.

In the prior art, the shift amount of the substrate stage 105 (substrate104) from the optimum exposure position is obtained based on the optimumexposure position, the initial position of the substrate stage 105, andthe measurement result of the measurement unit MU. The target valueregarding driving of the substrate stage 105 is obtained by applying, tothe shift amount thus obtained, the respective gains of the PIDcontroller 501, the filter 502 (for example, a cutoff frequency oflow-pass filter processing), and the limited driving amount 503 of thesubstrate stage 105. The substrate stage 105 is driven so that theposition of the substrate 104 in the Z-axis direction is positioned atthe optimum exposure position while feeding back the position (currentposition) of the substrate stage 105 obtained from the interferometer124 to the target value regarding driving of the substrate stage 105.

Then, in the prior art, the height-direction positions of measurementobject portions (not shown) in the shot region 402 are measuredsequentially. Once the exposure slit 202 reaches the shot region 402,the mask 102 is illuminated with light from the light source via theillumination optical system 106, and the shot region 402 is exposedwhile performing measurement by the measurement unit MU and driving ofthe substrate stage 105 in the Z-axis direction sequentially. Once theexposure slit 202 passes through the shot region 402, a process forexposing the shot region 403 is started, the substrate stage 105 isdriven in the X-axis direction while decelerating it in the Y-axisdirection, and then accelerates the substrate stage 105 in the Y-axisdirection.

FIG. 6A is a timing chart showing the relationship between a time periodand the position of the substrate stage 105 in the Z-axis direction whenthe substrate stage 105 moves along the trajectory shown in FIGS. 4A to4C in the prior art. In FIG. 6A, the ordinate represents the position ofthe substrate stage 105 in the Z-axis direction, and the abscissarepresents the time period (time).

In FIG. 6A, time t0 is time at which the first driving is started, andtime t1 is time at which the first driving is ended. Time t2 is time atwhich the second driving is started, and time t3 is time at which thesecond driving is ended. Time t4 is time at which the exposure slit 202reaches the shot region 402. Ztarget is an optimum exposure position.Zlimit 1 is a limited driving amount of the substrate stage 105 in thefirst driving, that is, a driving amount of the substrate stage 105 inthe Z-axis direction allowed in the first driving. In the first driving,the driving amount of the substrate stage 105 in the Z-axis direction islimited so that the driving amount of the substrate stage 105 fallswithin Zlimit 1. Zlimit 2 is a limited driving amount of the substratestage 105 in the second driving, that is, a driving amount of thesubstrate stage 105 in the Z-axis direction allowed in the seconddriving. In the second driving, the driving amount of the substratestage 105 in the Z-axis direction is limited so that the driving amountof the substrate stage 105 falls within Zlimit 2.

Note that a time period dt01 (from the time t0 to the time t1) requiredfor the first driving and a time period dt23 (from the time t2 to thetime t3) required for the second driving have a relationship ofdt01=dt23. The limited driving amount Zlimit 1 in the first driving andthe limited driving amount Zlimit 2 in the second driving have arelationship of Zlimit 1=Zlimit 2.

FIG. 6B is a timing chart in which the control deviation of thesubstrate stage 105 is added to the relationship between the time periodand the position of the substrate stage 105 in the Z-axis directionshown in FIG. 6A. FIG. 6B shows a difference between the actual positionof the substrate stage 105 and a target position 601 of the substratestage 105 in the Z-axis direction at the respective times, that is, acontrol deviation 602 in the Z-axis direction. If the target position601 of the substrate stage 105 in the Z-axis direction and the actualposition of the substrate stage 105 in the Z-axis direction match, thecontrol deviation 602 of the substrate stage 105 becomes 0.

Referring to FIG. 6B, immediately after the time t0 at which the firstdriving is started, the change amount of the target position 601 islarge, and the change amount of the control deviation 602 is also large.As the time t1 at which the first driving is ended approaches, thechange amount of the target position 601 decreases, and the changeamount of the control deviation 602 also decreases. After the time t2 atwhich the second driving is started, however, the change amount of thetarget position 601 and the control deviation 602 increase again. As thetime t3 at which the second driving is ended approaches, the changeamount of the target position 601 decreases, the change amount of thecontrol deviation 602 also decreases, and the control deviation 602converges to 0. However, if the substrate stage 105 is driven by adriving amount that exceeds the response of the substrate stage 105(driving amount that exceeds the limited driving amount), the controldeviation of the substrate stage 105 increases. For example, at the timet4 when the exposure slit 202 reaches the shot region 402, the controldeviation 602 remains greatly without converging to 0. This means astate in which the position of the substrate stage 105 in the Z-axisdirection is shifted from the optimum exposure position. Therefore, ifexposure of the shot region 402 is started at the time t4 with thiscontrol deviation 602 remaining greatly, that causes a resolution errorby defocus.

To prevent this, in the embodiment, the main control unit 127 changes acontrol parameter in the first driving and a control parameter in thesecond driving, and controls driving of the substrate stage 105 in theZ-axis direction. More specifically, the main control unit 127 makes thedriving amount of the substrate stage 105 in the Z-axis direction in thefirst driving larger than half a distance corresponding to thedifference between the optimum exposure position and the positions ofthe measurement object portions in the Z-axis direction measured at themeasurement points 209 to 211 of the second measurement unit, as will bedescribed later.

Control regarding driving of the substrate stage 105 to position theposition of the substrate 104 in the Z-axis direction at the optimumexposure position in the embodiment will be described with reference toFIGS. 7A and 7B, and FIG. 8. FIG. 7A is a timing chart showing therelationship between a time period and the position of the substratestage 105 in the Z-axis direction when the substrate stage 105 movesalong the trajectory shown in FIGS. 4A to 4C in the embodiment. In FIG.7A, the ordinate represents the position of the substrate stage 105 inthe Z-axis direction, and the abscissa represents the time period.

In FIG. 7A, the time t0 is the time at which the first driving isstarted, and time t1′ is time at which the first driving is ended. Thetime t2 is the time at which the second driving is started, and time t3′is time at which the second driving is ended. The time t4 is the time atwhich the exposure slit 202 reaches the shot region 402. That is,exposure to a shot region to be exposed is started from the time t4, andit is thus preferable that the control deviation of the substrate stage105 converges to an allowable value or smaller by the time t4. Ztargetis the optimum exposure position. Zlimit 1′ is a limited driving amountof the substrate stage 105 in the first driving, that is, a drivingamount of the substrate stage 105 in the Z-axis direction allowed in thefirst driving. In the first driving, the main control unit 127 limitsthe driving amount of the substrate stage 105 in the Z-axis direction sothat the driving amount of the substrate stage 105 falls within Zlimit1′. Zlimit 2′ is a limited driving amount of the substrate stage 105 inthe second driving, that is, a driving amount of the substrate stage 105in the Z-axis direction allowed in the second driving. In the seconddriving, the main control unit 127 limits the driving amount of thesubstrate stage 105 in the Z-axis direction so that the driving amountof the substrate stage 105 falls within Zlimit 2′.

Note that Ztarget shown in FIG. 7A has the same amount as Ztarget shownin FIG. 6A. A time period from the time t0 to the time t4 shown in FIG.7A is equal to a time period from the time t0 to the time t4 shown inFIG. 6A. Thus, FIG. 7A and FIG. 6A are the same in time period from thestart of control driving of the substrate stage 105 to position theposition of the substrate 104 in the Z-axis direction at the optimumexposure position to the start of exposure and driving amount of thesubstrate stage 105 in the Z-axis direction.

In FIG. 7A, a time period dt01′ (from the time t0 to the time t1′)required for the first driving and a time period dt23′ (from the time t2to the time t3′) required for the second driving have a relationship ofdt01′<dt23′. The limited driving amount Zlimit 1′ in the first drivingand the limited driving amount Zlimit 2′ in the second driving have arelationship of Zlimit 1′>Zlimit 2′. As described above, the maincontrol unit 127 makes the time period required for the first drivingshorter than the time period required for the second driving and makesthe limited driving amount Zlimit 1′ in the first driving larger thanthe limited driving amount Zlimit 2′ in the second driving.

FIG. 7B is a timing chart in which the control deviation of thesubstrate stage 105 is added to the relationship between the time periodand the position of the substrate stage 105 in the Z-axis directionshown in FIG. 7A. FIG. 7B shows a control deviation 702 from a targetposition 701 of the substrate stage 105 in the Z-axis direction. If thetarget position 701 of the substrate stage 105 in the Z-axis directionand the actual position of the substrate stage 105 in the Z-axisdirection match, the control deviation 702 of the substrate stage 105becomes 0.

Referring to FIG. 7B, immediately after the time t0 at which the firstdriving is started, the change amount of the target position 701 islarge, and the change amount of the control deviation 702 is also large.As the time t1′ at which the first driving is ended approaches, thechange amount of the target position 701 decreases, but the changeamount of the control deviation 702 remains large because the substratestage 105 is driven greatly in a short time period. Immediately afterthe time t2 at which the second driving is started, the change amount ofthe target position 701 is small, and thus the control deviation 702newly caused by the second driving also becomes small. Therefore, acontrol deviation caused by the first driving becomes predominant in thecontrol deviation 702 from the time t1′. On the other hand, a timeperiod from the time t1′ to the time t4 is longer than a time periodfrom the time t1 to the time t4 shown in FIGS. 6A and 6B. Consequently,the control deviation 702 continues to converge to 0 and converges to 0at the time t4. This means a state in which the position of thesubstrate stage 105 in the Z-axis direction matches the optimum exposureposition. Therefore, the resolution error by defocus is not generatedeven if exposure of the shot region 402 is started at the time t4.

A control parameter may be set so as to satisfy the time period dt01′(from the time t0 to the time t1′) required for the first driving>thetime period dt23′ (from the time t2 to the time t3′) required for thesecond driving. This makes it possible to secure a long settling timeperiod between the end of the second driving and the start of exposure,and thus to reduce the control deviation at time when exposure isstarted.

FIG. 8 is a schematic block diagram showing a control system regardingdriving of the substrate stage 105 in the embodiment (main control unit127). An example to which PID control is applied will be described, asin the prior art. The control system includes a first PID controller801, a first filter 802, a first limited driving amount 803 of thesubstrate stage 105, a second PID controller 804, a second filter 805,and a second limited driving amount 806 of the substrate stage 105.

In FIG. 8, the initial position of the substrate stage 105 is theposition of the substrate stage 105 in the Z-axis direction before thefirst driving or second driving of the substrate stage 105 to positionthe position of the substrate 104 in the Z-axis direction at the optimumexposure position is started. The switch SW1 is the switch whichswitches the measurement points of the measurement unit MU used tomeasure the height-direction positions of the measurement objectportions in the shot region of the substrate 104. For example, in thefirst driving shown in FIG. 4B, the switch SW1 is switched such that thesubstrate stage 105 is driven (controlled) based on the measurementresults at the measurement points 209 to 211 as the second measurementunit. In the second driving shown in FIG. 4C, the switch SW1 is switchedsuch that the substrate stage 105 is driven (controlled) based on themeasurement results at the measurement points 206 to 208 as the firstmeasurement unit. The first PID controller 801 is a controllerconfigured to control driving of the substrate stage 105 in the Z-axisdirection in the first driving, and includes the first P gain(proportional gain), the first D gain (derivative gain), and the first Igain (integral gain). The first filter 802 is a filter (for example, acutoff frequency of low-pass filter processing) in the first driving.The first limited driving amount 803 is the limited driving amount (inthe embodiment, Zlimit 1′) of the substrate stage 105 in the firstdriving. The second PID controller 804 is a controller configured tocontrol driving of the substrate stage 105 in the Z-axis direction inthe second driving, and includes the second P gain different from thefirst P gain, the second D gain different from the first D gain, and thesecond I gain different from the first I gain. The second filter 805 isa filter (for example, a cutoff frequency of low-pass filter processing)in the second driving. The second limited driving amount 806 is thelimited driving amount (in the embodiment, Zlimit 2′) of the substratestage 105 in the second driving. A switch SW2 is a switch which switchesthe PID controllers, the filters, and the limited driving amounts usedbetween the first driving and the second driving. For example, in thefirst driving shown in FIG. 4B, the switch SW2 is switched such that thefirst PID controller 801, the first filter 802, and the first limiteddriving amount 803 are used. In the second driving shown in FIG. 4C, theswitch SW2 is switched such that the second PID controller 804, thesecond filter 805, and the second limited driving amount 806 are used.

In the first driving, if the driving amount of the substrate stage 105input from the first filter 802 is equal to or smaller than the firstlimited driving amount 803, the driving amount is output without anychange. On the other hand, in the first driving, if the driving amountof the substrate stage 105 input from the first filter 802 is largerthan the first limited driving amount 803, the first limited drivingamount 803 is output as the driving amount of the substrate stage 105.Similarly, in the second driving, if the driving amount of the substratestage 105 input from the second filter 805 is equal to or smaller thanthe second limited driving amount 806, the driving amount is outputwithout any change. On the other hand, in the second driving, if thedriving amount of the substrate stage 105 input from the second filter805 is larger than the second limited driving amount 806, the secondlimited driving amount 806 is output as the driving amount of thesubstrate stage 105.

Based on the optimum exposure position, the initial position of thesubstrate stage 105, and the measurement result of the measurement unitMU, the main control unit 127 obtains the shift amount of the substratestage 105 (substrate 104) from the optimum exposure position. In thefirst driving, the target value regarding driving of the substrate stage105 is obtained by applying, to the shift amount thus obtained, therespective gains of the first PID controller 801, the first filter 802,and the first limited driving amount 803. In the second driving, thetarget value regarding driving of the substrate stage 105 is obtained byapplying the respective gains of the second PID controller 804, thesecond filter 805, and the second limited driving amount 806 to theshift amount thus obtained. The position of the substrate 104 in theZ-axis direction is positioned at the optimum exposure position by thefirst driving and the second driving while feeding back the position(current position) of the substrate stage 105 obtained from theinterferometer 124 to the target value regarding driving of thesubstrate stage 105.

According to the embodiment, it is possible to suppress the controldeviation of the substrate stage 105 at an exposure start even if thesubstrate stage 105 has to be driven in a short time period and by alarge driving amount in order to position the position of the substrate104 in the Z-axis direction at the optimum exposure position. Therefore,the exposure apparatus 100 can reduce the resolution error by defocus.

Control parameters changed between the first driving and the seconddriving may be gains. The response of the substrate stage 105 in thefirst driving is increased by making the D gain of the first PIDcontroller 801 in the first driving higher than the D gain of the secondPID controller 804 in the second driving. A steady state deviation inthe second driving is suppressed by making the I gain of the first PIDcontroller 801 in the first driving smaller than the integral gain ofthe second PID controller 804 in the second driving. It is possible, bychanging the gains in the first driving and the second driving asdescribed above, to make the driving amount of the substrate stage 105in the Z-axis direction in the first driving larger than that in thesecond driving. This makes it possible to suppress the control deviationof the substrate stage 105 at the exposure start and to reduce theresolution error by defocus.

Control parameters changed between the first driving and the seconddriving may be cutoff frequencies (filter constants) in low-pass filterprocessing. A case in which, for example, control data for controllingdriving of the substrate stage 105 in the Z-axis direction is generatedby using each of the first filter 802 and the second filter 805 will beexamined. In this case, low-pass filter processing having a cutofffrequency is performed on each of the first difference data between theoptimum exposure position and the measurement result of the secondmeasurement unit, and the second difference data between the optimumexposure position and the measurement result of the first measurementunit. At this time, the cutoff frequency of the low-pass filterprocessing performed on the first difference data is made higher thanthat on the second difference data. More specifically, the response ofthe substrate stage 105 in the first driving is increased by setting thecutoff frequency of the first filter 802 used in the first driving high.An increase in control deviation in the second driving is suppressed bysetting the cutoff frequency of the second filter 805 used in the seconddriving low. It is possible, by changing the cutoff frequencies of thelow-pass filter processing in the first driving and the second drivingas described above, to make the driving amount of the substrate stage105 in the Z-axis direction in the first driving larger than that in thesecond driving. This makes it possible suppress the control deviation ofthe substrate stage 105 at the exposure start and to reduce theresolution error by defocus.

Control parameters changed between the first driving and the seconddriving may be the type of functions used for interpolation when thetrajectory of the substrate stage 105 with respect to its position inthe Z-axis direction is obtained. FIG. 9 is a timing chart showing thetrajectory of the substrate stage 105 with respect to its position inthe Z-axis direction. In FIG. 9, the ordinate represents the position ofthe substrate stage 105 in the Z-axis direction, and the abscissarepresents a time period. Time t5 is time at which driving of thesubstrate stage 105 in the Z-axis direction is started. Time t6 is timeat which driving of the substrate stage 105 in the Z-axis direction isended. For example, when the target value of driving of the substratestage 105 to position the position of the substrate 104 in the Z-axisdirection at the optimum exposure position is obtained, in the firstdriving, interpolation is performed such that the change amount of thatdriving amount becomes a steep trajectory 901, increasing the responseof the substrate stage 105 in the first driving. In the first driving,for example, interpolation is performed on a time period from the timet5 with a linear function. In the second driving, interpolation isperformed so that the change amount of the driving amount of thesubstrate stage 105 becomes a moderate trajectory 902, suppressing theincrease in control deviation of the substrate stage 105 in the seconddriving. In the second driving, for example, interpolation is performedon a time period from the time t6 with a saturation function (such as aroot function). In other words, the maximum value of the change amountof the driving amount of the substrate stage 105 with respect to thetime period in the first driving is made larger than that in the seconddriving. As described above, the type of functions used forinterpolation when the trajectory of the substrate stage 105 is obtainedin the first driving and the second driving is changed. This makes itpossible to make the driving amount of the substrate stage 105 in theZ-axis direction in the first driving larger than that in the seconddriving. It is therefore possible to suppress the control deviation ofthe substrate stage 105 at the exposure start and to reduce theresolution error by defocus.

The response of the substrate stage 105 to the Z-axis direction may bedifferent at the rotation about the X-axis, the rotation about theY-axis, and the position in the Z-axis direction. In this case, controlparameters changed between the first driving and the second driving maybe changed with respect to the rotation about the X-axis, the rotationabout the Y-axis, and the position in the Z-axis direction.

Control parameters changed between the first driving and the seconddriving can combine the above-described parameters freely. Note that inthe embodiment, the PID controller and the filter are provided for eachof the first driving and the second driving, as shown in FIG. 8.However, the present invention is not limited to this. An arrangementmay be possible in which, for example, control parameters are changedbetween the first driving and the second driving for one PID controllerand one filter.

An operation in the exposure apparatus 100, that is, the exposureprocess will be described with reference to FIG. 10. As described above,the exposure process is performed by comprehensively controlling therespective units of the exposure apparatus 100 by the main control unit127.

In step S1002, the substrate 104 is loaded into the exposure apparatus100. More specifically, the substrate 104 is conveyed by a conveyinghand (not shown) and held by the substrate stage 105.

In step S1004, pre-alignment (pre-measurement and correction) for globalalignment is performed. More specifically, the shift amount such as therotation error of the substrate 104 is measured and corrected using alow-magnification field alignment microscope (not shown) so that analignment mark on the substrate 104 falls within the measurement rangeof a high-magnification field alignment microscope (not shown) to beused in global alignment.

In step S1006, global tilt is performed. More specifically, as shown inFIG. 11, the measurement unit MU measures the height-direction positionsof sample shot regions 1101 among a plurality of shot regions of thesubstrate 104. The global tilt of the substrate 104 is calculated andcorrected based on the height-direction positions of the sample shotregions 1101 measured by the measurement unit MU.

In step S1008, pre-adjustment is performed for measurement of theheight-direction position of the substrate 104 during exposure (duringscanning of the mask stage 103 and substrate stage 105). Pre-adjustmentincludes, for example, adjustment of the light amount of the lightsource 110 of each measurement unit MU, storage of a pattern step in theshot region of the substrate 104, and the like. Pre-adjustment isperformed on the measurement unit MU including the measurement points203 to 217.

In step S1010, the projection optical system 101 is adjusted. Morespecifically, the tilt of the projection optical system 101, thecurvature of field, and the like are obtained using a light amountsensor and reference mark (neither is shown) arranged on the substratestage 105, and a reference plate (not shown) arranged on the mask stage103. For example, the light amount sensor arranged on the substratestage 105 measures a change of the amount of exposure light when thesubstrate stage 105 is scanned in the X-, Y-, and Z-axis directions. Theshift amount of the reference mark with respect to the reference plateis obtained based on the change of the amount of exposure light, and theprojection optical system 101 is adjusted.

In step S1012, global alignment is performed. More specifically, thealignment mark of the substrate 104 is measured using ahigh-magnification field alignment microscope, obtaining the shiftamount of the overall substrate 104 and a shift amount common torespective shot regions. To measure the alignment mark at high accuracy,the alignment mark needs to be positioned at a position (best contrastposition) at which the contrast of the alignment mark becomes best.Measurement of the best contrast position uses the measurement unit MUand an alignment microscope. For example, the substrate stage 105 isdriven to a predetermined height (position in the Z-axis direction), thealignment microscope measures the contrast, and the measurement unit MUmeasures the height of the substrate 104 in the Z-axis direction. Thisprocess is repeated. At this time, a contrast measurement resultcorresponding to each position of the substrate stage 105 in the Z-axisdirection and the measurement result of the position of the substrate104 in the Z-axis direction are saved in association with each other.Then, a position of the substrate stage 105 in the Z-axis directionwhere the contrast becomes highest is obtained based on a plurality ofcontrast measurement results and is defined as a best contrast position.

In step S1014, the exposure object shot region of the substrate 104 isexposed. More specifically, the measurement unit MU measures theheight-direction positions of measurement object portions in theexposure object shot region, and exposes the exposure object shot regionwhile positioning the position of the substrate 104 in the Z-axisdirection at the optimum exposure position by the substrate stage 105.Driving of the substrate stage 105 to position the position of thesubstrate 104 in the Z-axis direction at the optimum exposure positionis performed by the first driving and the second driving, as describedabove. At this time, the driving amount of the substrate stage 105 inthe Z-axis direction in the first driving is made larger than half thedistance corresponding to the difference between the optimum exposureposition and the positions of the measurement object portions in theZ-axis direction measured at the measurement points 209 to 211 of thesecond measurement unit.

In step S1016, the substrate 104 is unloaded from the exposure apparatus100. More specifically, the exposed substrate 104 is received from thesubstrate stage 105 by the conveying hand (not shown), and conveyedoutside the exposure apparatus 100.

A method of manufacturing an article according to the embodiment of thepresent invention is suitable for manufacturing an article, for example,a device (a semiconductor device, a magnetic storage medium, a liquidcrystal display element, or the like). The manufacturing methodincludes, using the exposure apparatus 100, a step of exposing asubstrate coated with a photosensitive agent and a step of developingthe exposed substrate. The manufacturing method can also include otherknown steps (oxidation, deposition, vapor deposition, doping,planarization, etching, resist removal, dicing, bonding, packaging, andthe like). The method of manufacturing the article according to theembodiment is superior to a conventional method in at least one of theperformance, quality, productivity, and production cost of the article.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-180906 filed on Sep. 15, 2016 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An exposure apparatus for transferring a pattern of a mask onto a substrate by exposing the substrate while scanning the mask and the substrate, the apparatus comprising: a stage configured to hold and move the substrate; a control unit configured to control movement of the stage; a first measurement unit configured to measure a position, in a height direction, of a shot region of the substrate held by the stage before the shot region reaches an exposure area where the shot region is exposed; and a second measurement unit configured to measure the position of the shot region in the height direction prior to the first measurement unit, wherein the control unit: controls the stage to perform: first driving where the substrate is driven in the height direction based on a measurement result of the second measurement unit; and second driving where the substrate is driven in the height direction based on a measurement result of the first measurement unit after the second measurement unit measures the position of the shot region in the height direction and until the shot region reaches the exposure area; makes a second driving amount of the stage in the height direction in the second driving smaller than a first driving amount of the stage in the height direction in the first driving; controls the stage so that the position of the shot region in the height direction is positioned at a first target position different from a second target position of the shot region in the height direction by the first driving and is positioned at the second target position by the second driving; and makes a time period required for the first driving from the position of the shot region in the height direction measured by the second measurement unit to the first target position shorter than a time period required for the second driving from the position of the shot region in the height direction measured by the first measurement unit to the second target position.
 2. The apparatus according to claim 1, wherein the control unit: includes a PID controller configured to control driving of the stage in the height direction, makes a derivative gain of the PID controller in the first driving higher than a derivative gain of the PID controller in the second driving.
 3. The apparatus according to claim 2, wherein the controller makes an integral gain of the PID controller in the first driving smaller than an integral gain of the PID controller in the second driving.
 4. The apparatus according to claim 1, wherein the control unit: performs low-pass filter processing having a cutoff frequency on each of first difference data between the second target position and the position of the shot region in the height direction measured by the second measurement unit, and second difference data between the second target position and the position of the shot region in the height direction measured by the first measurement unit to generate control data for controlling driving of the stage in the height direction; and makes the cutoff frequency of the low-pass filter processing performed on the first difference data higher than the cutoff frequency of the low-pass filter processing performed on the second difference data.
 5. The apparatus according to claim 1, wherein the control unit makes a maximum value of a change amount of the first driving amount of the stage with respect to a time period in the first driving larger than a maximum value of a change amount of the second driving amount of the stage with respect to a time period in the second driving.
 6. The apparatus according to claim 1, further comprising: a projection optical system configured to project the pattern of the mask onto the substrate, wherein a position of an image plane of the projection optical system comes to the second target position.
 7. The apparatus according to claim 1, wherein the first measurement unit and the second measurement unit have the same measurement accuracy in measurement of the position of the shot region in the height direction.
 8. The apparatus according to claim 1, wherein the first measurement unit and the second measurement unit have the same configuration for measuring the position of the shot region in the height direction.
 9. A method of manufacturing an article, the method comprising the steps of: forming a pattern on a substrate using an exposure apparatus; and developing the exposed substrate to manufacture the article, wherein the exposure apparatus transfers a pattern of a mask onto the substrate by exposing the substrate while scanning the mask and the substrate, and includes: a stage configured to hold and move the substrate; a control unit configured to control movement of the stage; a first measurement unit configured to measure a position, in a height direction, of a shot region of the substrate held by the stage before the shot region reaches an exposure area where the shot region is exposed; and a second measurement unit configured to measure the position of the shot region in the height direction prior to the first measurement unit, wherein the control unit: controls the stage to perform: first driving where the substrate is driven in the height direction based on a measurement result of the second measurement unit; and second driving where the substrate is driven in the height direction based on a measurement result of the first measurement unit after the second measurement unit measures the position of the shot region in the height direction and until the shot region reaches the exposure area; makes a second driving amount of the stage in the height direction in the second driving smaller than a first driving amount of the stage in the height direction in the first driving; controls the stage so that the position of the shot region in the height direction is positioned at a first target position different from a second target position of the shot region in the height direction by the first driving and is positioned at the second target position by the second driving; and makes a time period required for the first driving from the position of the shot region in the height direction measured by the second measurement unit to the first target position shorter than a time period required for the second driving from the position of the shot region in the height direction measured by the first measurement unit to the second target position.
 10. An exposure apparatus for transferring a pattern of a mask onto a substrate by exposing the substrate, the apparatus comprising: a stage configured to hold and move the substrate; a control unit configured to control movement of the stage; a first measurement unit configured to measure a position, in a height direction, of a shot region of the substrate held by the stage before the shot region reaches an exposure area where the shot region is exposed; and a second measurement unit configured to measure the position of the shot region in the height direction prior to the first measurement unit, wherein the control unit: controls the stage to perform: first driving where the substrate is driven in the height direction based on a measurement result of the second measurement unit; and second driving where the substrate is driven in the height direction based on a measurement result of the first measurement unit after the second measurement unit measures the position of the shot region in the height direction and until the shot region reaches the exposure area; makes a second driving amount of the stage in the height direction in the second driving smaller than a first driving amount of the stage in the height direction in the first driving; controls the stage so that the position of the shot region in the height direction is positioned at a first target position different from a second target position of the shot region in the height direction by the first driving and is positioned at the second target position by the second driving; and makes a time period required for the first driving from the position of the shot region in the height direction measured by the second measurement unit to the first target position shorter than a time period required for the second driving from the position of the shot region in the height direction measured by the first measurement unit to the second target position.
 11. A method of manufacturing an article, the method comprising the steps of: forming a pattern on a substrate using an exposure apparatus; and developing the exposed substrate to manufacture the article, wherein the exposure apparatus transfers a pattern of a mask onto the substrate by exposing the substrate, and includes: a stage configured to hold and move the substrate; a control unit configured to control movement of the stage; a first measurement unit configured to measure a position, in a height direction, of a shot region of the substrate held by the stage before the shot region reaches an exposure area where the shot region is exposed; and a second measurement unit configured to measure the position of the shot region in the height direction prior to the first measurement unit, wherein the control unit: controls the stage to perform: first driving where the substrate is driven in the height direction based on a measurement result of the second measurement unit; and second driving where the substrate is driven in the height direction based on a measurement result of the first measurement unit after the second measurement unit measures the position of the shot region in the height direction and until the shot region reaches the exposure area; makes a second driving amount of the stage in the height direction in the second driving smaller than a first driving amount of the stage in the height direction in the first driving; controls the stage so that the position of the shot region in the height direction is positioned at a first target position different from a second target position of the shot region in the height direction by the first driving and is positioned at the second target position by the second driving; and makes a time period required for the first driving from the position of the shot region in the height direction measured by the second measurement unit to the first target position shorter than a time period required for the second driving from the position of the shot region in the height direction measured by the first measurement unit to the second target position. 